Behavioral effects of isolation in the rat

Abstract

Ab.traetMale albino rats were raised either invidually (N = 13) or in groups (N = 12) from weaning at 21 days of age until they were tested at 111 days of age. Experimenter ratings and a "timidity" test showed the isolated Ss to be more emotional than group-raised Ss. No significant differences were found on startle or activity tests. ProbleDlAccording to Hatch et al (1963), after being housed for three months in an individual cage, "the isolated rat is a nervous, aggressive intractable animal." Objective tests, such as the open field and the emergence or "timidity" test (Ader & Friedman,1964; Hahn,1965; Stern, et aI, 1960) also support the conclusion that isolated rats are more emotional than group-housed rats. The purpose of the present study was to replicate some of the findings with respect to emotionality and to determine, by means of a startle test, whether the general level of arousal is higher in animals which have been isolated. MethodAt weaning (21 days of age), 30 male albino rats were assigned to either a group (8 or 7 Ss/cage) or an individual cage using a split litter control. The group cages measured 9-1/2 by 7 by 24 in and the single cages were 7 by 7 by 9-1/2 in. As a result of disease or experimenter error two isolated and three group-housed Ss were lost before testing. Animals were housed under standard laboratory conditions with food and water ad lib in external hoppers and bottles.At 111 days of age, Ss in group cages were put into single cages which were randomly distributed among the cages of Ss which had been raised in isolation. Each cage was individually numbered, but . in no way could the cages be differentiated by group. About 1 hr. later, an E who had not taken part in assigning grouped Ss to single cages rated the Ss on a 6-point scale for emotionality. The test involved picking up the S (gloved hand over the S's back), plaCing it on an adjacent table and then replacing it in its cage. The following ratings were applied: 0 -S made no attempt to escape from E and did not vocalize or jump; 1 -startle response on first attempt to handle S, but no vocalization or vigorous escape attempts; 2 -startle and vocalization; 3 -startle, greater vocalization and vigorous escape attempts; 4 -extreme vocalization and struggling, defecation; 5 -.same as 4

Contrasting effects of group housing and isolation on subsequent open field exploration in laboratory rats

“…Previous studies have reported conflicting results: Stern et al (1960), Thiessen et al (1962), Thiessen (1963), and Moyer & Korn (1965) all showed that group-housing leads to an increase in open field activity compared with isolation. The reverse was found by Essman (1966) and Weltman et al (1966).…”

“…Besides providing evidence concerning the possible role of social factors in population control (Chrlstian & Davis, 1964;Thiessen, 1964), this area of research has stimulated interest from workers more concerned with experimental psychology (e.g., Essman, 1966Essman, , 1968Moyer & Korn, 1965). The latter approach is characterized by investigations which sacrifice simulation of the natural environment for a greater degree of experimental control, and by theoretical discussions which consider the mechanisms involved in the response of the dependent variables to differences in the social environment (e.g., Welch, 1964).…”

The effects of age and isolation period on two phases of behavioral response to foot shock in isolation‐reared rats

“…Isolation-reared rats show excessive reactivity to handling (Ader, Kreutner, & Jacobs, 1963;Hatch, Balazs, Wiberg, & Grice, 1963), increased timidity (Moyer & Korn, 1965), and enhanced emotionality (DaSilva, Ferreira, Carobrez, & Morato, 1996;Koch & Arnold, 1972). These phenomena are referred to as ''the isolation stress syndrome'' (Hatch et al, 1965;Holson, Scallet, Ali, & Turner, 1991).…”

“…Rats reared in social isolation after weaning have been considered as an animal model of chronic stress since isolation rearing could be an experience that is an ecologically unnatural situation for this species (Moyer & Korn, 1965). Isolation-reared rats show excessive reactivity to handling (Ader, Kreutner, & Jacobs, 1963;Hatch, Balazs, Wiberg, & Grice, 1963), increased timidity (Moyer & Korn, 1965), and enhanced emotionality (DaSilva, Ferreira, Carobrez, & Morato, 1996;Koch & Arnold, 1972).…”

Social facilitation and sensory deprivation in operant behavior of rats

“…In short, it is not clear under what circumstances social facilitation occurs and what influence it may have on learning and stress. Moyer & Korn (1965), for instance, have shown that isolated albino rats are more emotional than group-raised Ss. Open field tests have also revealed that isolated Ss are more emotional than group-housed rats (Hahn, 1965).…”